Channel estimation apparatus and method for adaptive channel allocation in an orthogonal frequency division multiple access system

Abstract

A method and apparatus for defining at least one subcarrier as a subchannel, dividing a total frequency band into a plurality of subchannels, and allocating the subchannels to at least one mobile station in an OFDMA mobile communication system. The method includes receiving channel state information; comparing the received channel state information with a predetermined threshold, calculating an average occurrence length of a case in which the received channel state information is greater than the threshold, calculating a state hold prediction value, calculating an estimation value, sorting the calculated estimation values according to subchannels in order of their levels, and allocating subchannels according to the at least one mobile station in the sorted order.

1. A method for defining at least one subcarrier as a subchannel, dividing a total frequency band into a plurality of subchannels, and allocating the subchannels to at least one mobile station in an Orthogonal Frequency Division Multiple Access (OFDMA) wireless communication system, the method comprising the steps of:
 receiving channel state information of the subchannels from the at least one mobile station; 
 comparing the received channel state information with a predetermined threshold; 
 determining a number of cases in which the received channel state information is greater than the predetermined threshold; 
 calculating an average occurrence length of the case in which the received channel state information is greater than the predetermined threshold, from the determined values separately stored for the subchannels for a predetermined period; 
 calculating a state hold prediction value for a next state of which a channel state information is greater than the threshold, from the calculated average occurrence length; and 
 calculating an estimation value for the next state from the state hold prediction value and a current channel state value. 
 
   
   
     2. The method of  claim 1 , further comprises the steps of:
 sorting the calculated estimation values according to an order based on levels of the subchannels; and 
 allocating the subchannels according to the at least one mobile station in the sorted order. 
 
   
   
     3. The method of  claim 1 , wherein the channel state information includes a signal-to-noise ratio value measured from each of the at least one mobile station. 
   
   
     4. The method of  claim 1 , wherein the channel state information includes signal power measured from each of the at least one mobile station. 
   
   
     5. The method of  claim 1 , wherein the state hold prediction value is calculated by subtracting a current count value from the average occurrence length. 
   
   
     6. The method of  claim 1 , wherein the step of comparing the received channel state information with the predetermined threshold comprises the step of storing a current channel state as a G state, which indicates a good channel state, and counting a number of successive G states, if the received channel state information is greater than the threshold. 
   
   
     7. The method of  claim 6 , wherein the step of comparing the received channel state information with the predetermined threshold comprises the step of storing a current channel state as a B state, which indicates a bad channel state, and decreasing the accumulated count value, if the received channel state information is less than the threshold. 
   
   
     8. The method of  claim 7 , wherein the step of comparing the received channel state information with the predetermined threshold comprises the steps of:
 storing the current channel state as the B state, if the received channel state information is less than the threshold; and 
 initializing the accumulated count value, if a next channel state becomes the G state. 
 
   
   
     9. An apparatus for defining at least one subcarrier as a subchannel, dividing a total frequency band into a plurality of subchannels, and allocating the subchannels to at least one mobile station in an Orthogonal Frequency Division Multiple Access (OFDMA) wireless communication system, the apparatus comprising:
 a subchannel allocator for comparing channel state information received from the at least one mobile station with a predetermined threshold, determining a number of cases in which the received channel state information is greater than the predetermined threshold, estimating a channel state value for a next time from the determined number of cases stored for a predetermined period, and allocating the subchannels for the at least one mobile station. 
 
   
   
     10. The apparatus of  claim 9 , wherein the channel state information comprises a signal-to-noise ratio value measured from each of the at least one mobile station. 
   
   
     11. The apparatus of  claim 9 , wherein the channel state information comprises signal power measured from each of the at least one mobile station. 
   
   
     12. The apparatus of  claim 9 , wherein the subchannel allocator calculates an average occurrence length of a case in which the received channel state information is greater than the predetermined threshold, from the determined number of cases separately stored for the subchannels for the predetermined period, calculates a state hold prediction value for a next state of which a channel state information is greater than the predetermined threshold, from the calculated average occurrence length, calculates an estimation value for the next state from the state hold prediction value and a current channel state value, sorts the calculated estimation values according to the subchannels in an order based on levels of the subchannels, and allocates the subchannels according to the at least one mobile station in the sorted order. 
   
   
     13. The apparatus of  claim 9 , wherein in comparing received channel state information with the predetermined threshold, the subchannel allocator stores a current channel state as a G state, which indicates a good channel state, and determines a number of successive G states, if the received channel state information is greater than the predetermined threshold. 
   
   
     14. The apparatus of  claim 13 , wherein in comparing received channel state information with the predetermined threshold, the subchannel allocator stores a current channel state as a B state, which indicates a bad channel state, and decreases the determined count value, if the received channel state information is less than the predetermined threshold. 
   
   
     15. The apparatus of  claim 14 , wherein in comparing received channel state information with the predetermined threshold, the subchannel allocator stores the current channel state as the B state, if the received channel state information is less than the predetermined threshold, and initializes the determined value, if a next channel state becomes a G state. 
   
   
     16. The apparatus of  claim 9 , further comprising a subchannel mapper for receiving subchannel allocation information determined by the subchannel allocator, and mapping user data transmitted to the at least one mobile station to respective input points of an inverse fast Fourier transform (IFFT) module according to the received subchannel allocation information. 
   
   
     17. A method for defining at least one subcarrier as a subchannel, dividing a total frequency band into a plurality of subchannels, allocating the subchannels to at least one mobile station, and receiving transmitted data using the allocated subchannels in an Orthogonal Frequency Division Multiple Access (OFDMA) wireless communication system, the method comprising the steps of:
 comparing channel state information received from the at least one mobile station with a predetermined threshold; 
 counting a number of cases in which the received channel state information is greater than the predetermined threshold; 
 estimating a channel state value for a next time from the counted values stored for a predetermined period; 
 receiving subchannel allocation information allocated for the at least one mobile station; and 
 selecting a subchannel allocated thereto from subchannels received through the received subchannel allocation information. 
 
   
   
     18. The method of  claim 17 , wherein the channel state information includes a signal-to-noise ratio value measured from the at least one mobile station. 
   
   
     19. The method of  claim 17 , wherein the channel state information includes signal power measured from the at least one mobile station. 
   
   
     20. An apparatus for defining at least one subcarrier as a subchannel, dividing a total frequency band into a plurality of subchannels, allocating the subchannels to at least one mobile station, and receiving transmitted data using the allocated subchannels in an Orthogonal Frequency Division Multiple Access (OFDMA) wireless communication system, the apparatus comprising:
 a subchannel selector for comparing channel state information received from the at least one mobile station with a predetermined threshold, counting a number of cases in which the received channel state information is greater than the predetermined threshold, estimating a channel state value for a next time from the counted values stored for a predetermined period, receiving subchannel allocation information allocated for the at least one mobile station, and selecting a subchannel allocated thereto from subchannels received through the received subchannel allocation information. 
 
   
   
     21. The apparatus of  claim 20 , wherein the channel state information comprises a signal-to-noise ratio value measured from the at least one mobile station. 
   
   
     22. The apparatus of  claim 20 , wherein the channel state information comprises signal power measured from the at least one mobile station.